Difference Between Spontaneous and Induced Mutation

Mutations can occur due to a variety of reasons, such as deletion, insertion, or substitution of one or more nucleotides. When a purine nucleotide is replaced by a purine nucleotide, it is called a transition. Transversion occurs when a purine is replaced by a pyrimidine. Spontaneous and Induced Mutations are the two types of genetic mutations.

This Story also Contains

1. Mutation
2. Spontaneous Mutation
3. Induced Mutation
4. Difference between Spontaneous and Induced Mutation
5. Detection and Analysis of Mutations
6. Recommended Video on “Types of Mutations”
7. MCQs on Mutations & Their Features

Spontaneous mutations are those that occur naturally due to errors in the replication of DNA or DNA repair. It can also occur from natural, chemical, or biological processes. Induced mutations, on the other hand, are caused due to external factors, called mutagens. The mutagens could be chemicals or radiation, which damage the DNA. The difference between Spontaneous and Induced Mutations is an important topic in the chapter Evolution. It is an important chapter in the biology subject.

Mutation

A mutation is a change in the DNA sequence and affects the genetic information carried by that sequence. They can result from errors during DNA replication, exposure to mutagens, or spontaneous chemical changes in DNA. Changes may range from small nucleotide changes to large changes in chromosomes.

Spontaneous Mutation

Spontaneous mutations are those that occur naturally, with no external influence. The former can be the result of random errors in DNA replication or from spontaneous chemical changes of DNA within the cell.

Causes

• Replication errors of the DNA.

• Natural environmental factors, for example, radiation.

• Spontaneous chemical changes of DNA. For example, the deamination of cytosine to uracil.

• Examples of spontaneous mutations in nature are point mutations in bacterial populations.

Mechanism

• Misincorporation of nucleotides during DNA replication

• Tautomeric shifts, leading to mismatches in base pairing

• Spontaneous hydrolysis of the glycosidic bond in purine bases, that i, depurination.

• Deamination of cytosine into uracil or adenine into hypoxanthine

Consequences

• Beneficial mutations: Offer advantages, e.g., antibiotic resistance in bacteria.

• Neutral mutations: No effect is known on the fitness of an organism; they tend to be in non–coding regions.

• Harmful mutation: Genetic disorders or a decrease in the fitness of the organism.

Examples

• Lactose tolerance in humans is beneficial.

• Silent mutations in DNA.

• Sickle cell anaemia is due to a single nucleotide change in the haemoglobin gene, which is harmful.

Induced Mutation

Induced mutations are those occurring as the result of exposure to external factors, called mutagens. It will be a chemical, physical or biological agent that alters the sequence of DNA.

Causes

• Chemical mutagens: Benzene, formaldehyde, ethidium bromide

• Physical mutagens: UV radiation, X-rays, gamma rays

• Biological agents: Certain viruses and bacteria that insert their genetic material into the host genome.

Mechanism

• Chemical mutagens: can induce base modifications, insertions, deletions or cross-linking of DNA strands.

• Physical mutagens: can induce breaks in the DNA strands or thymine dimers

• Biological agents: can introduce their genetic material, interfering with normal gene activity.

Consequences

• Beneficial mutations: Used in biotechnology and research, e.g. development of strains of bacteria for the production of certain compounds.

• Neutral mutations: These may not have any observable effect on the organism.

• Harmful mutations: Can be oncogenic or cause other kinds of genetic diseases.

Examples

• Beneficial: Genetic engineering for herbicide resistance of crops.

• Neutral: Those are induced but do not have negative effects on the protein function.

• Harmful: Induced by radiation and sometimes causes cancer.

Difference between Spontaneous and Induced Mutation

The table below depicts the key differences between Spontaneous and Induced Mutation. Explore additional Differences and Comparisons Articles in Biology to expand your understanding.

Detection and Analysis of Mutations

There are various techniques for identifying mutations. They can be either by DNA sequencing, PCR, and gel electrophoresis. Those are explained below-

• DNA sequencing: Determines the exact sequence of nucleotides in a DNA molecule, allowing for the identification of mutations.

• PCR (Polymerase Chain Reaction): Amplifies specific DNA regions to detect and analyse mutations.

• Gel electrophoresis: Separates DNA fragments based on size, allowing for the detection of mutations such as insertions or deletions.

Recommended Video on “Types of Mutations”

MCQs on Mutations & Their Features

Q1. Which of the following statement is NOT correct ?

Option 1: Mutations provide variation upon which natural selection can act

Option 2: The vast majority of mutations produce alleles which are dominant

Option 3: Mutations arise spontaneously , infrequently and at random

Option 4: Mutation rate can be increased by artificial means

Correct answer: 2) The vast majority of mutations produce dominant alleles.

Explanation:

Mutation is a phenomenon that leads to changes in DNA sequences, causing alterations in an organism's genotype and phenotype. These changes may occur spontaneously or due to external factors such as radiation or chemicals. Mutations play an important role in evolution, genetic variation, and diseases.

Hence, the correct answer is option 2) The vast majority of mutations produce dominant alleles.

Q2. What is the difference between spontaneous and induced mutations?

Option 1: Spontaneous mutations occur due to external factors while induced mutations occur naturally.

Option 2: Spontaneous mutations are produced in response to specific external factors while induced mutations occur randomly.

Option 3: Spontaneous mutations occur randomly while induced mutations are produced in response to specific external factors.

Option 4: There is no difference between spontaneous and induced mutations.

Correct answer: 3) Spontaneous mutations occur randomly while induced mutations are produced in response to specific external factors.

Explanation:

1. Spontaneous Mutations:
These occur autonomously, without external intervention. They result from intrinsic errors in DNA replication or random chemical alterations, including deamination and tautomeric shifts, as well as natural background radiation. An example is a mistake made by DNA polymerase during cell division that repair mechanisms fail to rectify.

2. Induced Mutations:
Conversely, induced mutations are the result of external agents, known as mutagens, such as chemical substances, radiation, or biological entities. These mutagens elevate the mutation rate beyond the typical baseline observed in natural conditions. An illustration of this would be UV light inducing thymine dimers, or exposure to benzene, a known carcinogen, which inflicts DNA damage.

Hence, the correct answer is option 3) Spontaneous mutations occur randomly while induced mutations are produced in response to specific external factors.

Q3. Relative Biological Effectiveness (RBE) usually refers to damages caused by

Option 1: Low temperature

Option 2: High temperature

Option 3: Encephalitis

Option 4: Radiation

Correct answer: 4)Radiation.

Explanation:

Relative Biological Effectiveness (RBE) is a measure used in radiation biology to compare the biological damage caused by different types of radiation. It determines the effectiveness of a specific radiation type in causing harm compared to a reference radiation. RBE values vary for different radiation sources, with high-energy particles having higher RBE than low-energy photons. Thus, RBE is used to assess the damages caused by radiation.

Hence, the correct answer is option 4)Radiation.

Also Read:

• Practice MCQ on Mutation

• Evolution

• Mutation Theory